The present invention relates to an internet telephone apparatus, and more particularly to an internet telephone apparatus, in which an internet or an intranet mainly having an internet protocol (IP) is employed as a communication medium.
Conventionally, in such an internet telephone a compressed and coded audio data has been transmitted and received with a UDP (User Diagram Protocol) which does not conduct an error correction and request repeat control.
For example, as shown in International Telecommunication Union Telecommunication Standardization Sector Recommendation H. 323 and Recommendation H. 225, is described the technology for conducting an audio and video communication among the apparatuses via an IP network. A terminal described in this Recommendation H. 323 is a television telephone terminal conducting an audio/video communication, but is also defined as an internet telephone terminal since an operation of the video communication is optional.
FIG. 8 is a block diagram showing one example of a conventional internet telephone apparatus.
An internet telephone apparatus 100 is connected to a companion internet telephone apparatus through a network 114 to conduct the voice and image communication. An audio I/O 101 records voice of a speaker by means of a microphone and so forth to output a voice signal to an audio CODEC 102 and to simultaneously regenerate by means of a speaker and so forth the receiving voice signal that the audio CODEC 102 outputs.
The audio CODEC 102 processes for compressing and coding the voice signal that the audio I/O 101 outputs to output the compressed voice data to a H. 225 layer 112 through a reception channel delay 103. A video I/O 105 which is optional takes image of the speaker by means of a video camera and so forth to output an image signal to a video CODEC 104 and to simultaneously paint on a display device and so forth the receiving video signal that the video CODEC 104 outputs. A video CODEC 104 which is optional processes for compressing and coding the video signal that is input from the video I/O 105 to output the compressed image data to the H. 225 layer 112 through the reception channel delay 103. In the process for compressing and coding which is optional, either ITU-T H. 261 or ITU-T H. 263 is employed for compressing and coding of video.
The reception channel delay 103 generates delay when discrepancy between regeneration voice and paint video occurs, depending upon a transmission line situation, in case that the internet telephone apparatus conducts the audio/video communication with the companion internet telephone apparatus. A user data application and so forth 106 executes an application utilizing a user data channel of a television telephone apparatus. In a system controller UI 111 a system controller 107 negotiates on a call connection control to a companion terminal, an operational mode and so forth. The system controller 107 is constructed of a call controller 108, a H. 245 controller 109 and a RAS (Registration Admission Status) controller 110.
The call controller 108 conducts a call connection/disconnection control to/from the companion internet telephone apparatus according to the Recommendation H. 225. The H. 245 controller 109 negotiates with the companion internet telephone apparatus on the operational mode and so forth according to the Recommendation H. 245. The RAS controller 110 conducts a conference management and so forth to a gate keeper (GK). The H. 225 layer 112 inputs/outputs the compressed voice data from/to the audio CODEC 102, the compressed image data from/to the video CODEC 104 respectively to transmit/receive a TCP/IP data and a UDP/IP data to/from a Network I/F 113. The Network I/F 113 transmits/receives to/from the companion television telephone apparatus the TCP/IP data and the UDP/IP data that the H. 225 layer 112 inputs/outputs.
FIG. 9 is a detailed block diagram showing the H. 225 layer.
A RTP (Real Time Transfer Protocol) 120 processes for compressing and coding/expanding and decoding the compressed voice data that is input/output from/to the audio CODEC and the compressed image data that is input/output from/to the video CODEC to input/output the RTP data from/to the UDP layer. A RAS 121 inputs/outputs a RAS data from/to the UDP layer 122 based on a RAS control signal that is input/output from the RAS control. A UDP layer 122 inputs/outputs from/to an IP layer 127 the RTP data that is input/output from/to the RTP 120 and the RAS data that is input/output from/to the RAS 121.
A call signaling 123 inputs/outputs a call signaling data from/to a TCP layer 125 based on a call signaling signal that is input/output from/to a H. 225 control. A H. 245 section 124 inputs/outputs a H. 245 data from/to the TCP layer 125 based on H. 245 control information that is input/output from/to the H. 245 control. The TCP layer 125 inputs/outputs a call signaling data from/to the call signaling 123 and a H. 245 data from/to the H. 245 section to input/output a TCP data from/to a IP layer 127. The IP layer 127 inputs/outputs the TCP data from/to the TCP layer 125 and the UDP data from/to the UDP layer 122 to input/output the IP data from/to the network I/F.
Next, the operation of the prior art will be explained in reference to FIG. 8.
First, the system controller UI 111 and the system controller 107 communicate to the companion internet telephone to conduct a call connection for an audio communication. When the call is established, the audio I/O 101 records/regenerates voice, the audio CODEC 102 processes for compressing and coding/expanding and decoding voice, the compressed voice data is transmitted/received to/from the companion internet telephone apparatus, and thereby a voice communication is conducted.
Also, the operation of the H. 225 layer in this prior art will be explained in reference to with FIG. 9.
The compressed video data that is input/output from/to the RTP 120 has a RTP header added/removed in the RTP 120, is processed for a UDP protocol in the UDP layer 122, and then is transmitted/received as the UPI data to/from the companion internet telephone. Similarly, the compressed audio data that is input/output from/to the RTP 120 has the RTP header added/removed in the RTP 120, are processed for a UDP protocol processing in the UDP layer 122, and then is transmitted/received as the UDP data to/from the companion internet telephone.
However, this prior art includes the following problem to be solved.
This problem lies in interruption of voice that is received from the companion internet telephone in case that a network is confused.
The reason is that the UDP data might be destroyed or lost possibly when the network become confused since the compressed audio data is transmitted to the companion internet telephone apparatus as the UPD data that corresponded to the UDP protocol. In case that the destroyed UDP data has been received, the receiving compressed audio data could not be normally expanded and decoded, resulting in interruption of voice. Similarly, in case that the UDP data has been lost, the expanded and decoded data lacks in a real time for regenerating, resulting in interruption of voice.